1. Field of the Invention
This invention is concerned with wiring structures for use in electronic materials and more particularly with a method of producing such wiring structures in which a specified step process is incorporated to refill, by the bias ECR-CVD system (electron cyclotron reasonance-chemical vapor deposition), a selected metal of electrical conductivity into a connecting hole or aperture on a substrate.
2. Description of the Prior Art
Great concern has been directed toward minuteness and compactness in industrial sectors of electronic materials provided with wirings, such as for example semiconductive devices. The disclosures associated with semiconductors of such a minute and compact type are found for instance in JP-A 64-23554 and JP-A 64-10629. To cope with this trend, wiring structures to be assembled with semiconductors are required to be of reduced width. Minuteness requirements are made necessary and profound for those wirings obtained by refilling connecting holes commonly called contact holes or bearing holes. A keen demand therefore has been voiced for a means of enabling an electrically conductive material to be refilled into narrower connecting holes with utmost reliability.
Taking the above problem in view, it has been proposed to use as electrically conductive materials high melting point metals of sufficient heat resistance and great reliability among which tungsten (W) is typified. The W metal may preferably be turned into the form of films by the blanket W-CVD system in which a total wiring area to be coated is covered with a W film and thereafter is subjected to patterning. This system allows simultaneously for refilling of the connecting hole and for formation of the ultimate wiring and moreover exhibits process stability at a high level in contrast to the selective CVD system also for use in hole refilling. With use of the blanket W-CVD system now mentioned, W can be made into films with low resistance as compared to the sputtering system. Details with respect to those systems are taught in JP-A-62-219945.
The above blanket W-CVD is not necessarily satisfactory as it is susceptible in some cases to insufficient refilling. This is true for instance where a W plug is derived by refilling the connecting hole on a substrate, coupled with formation of a wiring by depositing W over the surface of the substrate. In that instance the connecting holes, if of great aspect ratios and hence layer depths, cause, due to inadequate step coverage during CVD, porous or void refilling.
Alternatively, the bias ECR-CVD system is known for the formation of a blanket W so as to improve hole refilling. This prior system, however, leaves the problem that the blanket W tends to be held adversely thick on the flat surface of the substrate.